1. Field of the Invention
This invention relates to a novel catalyst and process for the catalytic oxidation of gaseous carbonaceous emissions, in particular, gaseous carbonaceous emissions that include halogen-containing compounds, and more particularly organobromides.
2. Description of Related Art
The treatment of gaseous emissions containing volatile organic compounds and carbon monoxide has been of increasing concern in recent years. Thermal incineration, catalytic oxidation and adsorption are commonly used for removing these pollutants. Thermal incineration requires high operating temperatures and high capital cost facilities. If the gaseous stream also includes halogenated compounds, thermal incineration can evolve toxic halogenated compounds under certain operating conditions. In some instances, adsorption by adsorbents such as carbon is an alterative. However, this process does not destroy the pollutants, but merely concentrates them. Furthermore, adsorption efficiency can be adversely impacted by fluctuating concentrations of the gaseous components.
Catalytic oxidation is an energy efficient and economical way of destroying gaseous organic emissions. It operates at significantly lower temperatures and shorter residence time than thermal incineration and requires smaller reactors made of less expensive materials.
Methods for the catalytic oxidation of non-halogenated organic and halogenated organic compounds are well known in the art. For example, in the article by G. C. Bond and N. Sadeghi, "Catalyzed Destruction of Chlorinated Hydrocarbons" J. Appl. Chem. Biotechnol., 1975, 25, 241-248, it is reported that chlorinated hydrocarbons are converted to HCl and CO.sub.2 over platinum on gamma alumina catalyst.
U.S. Pat. Nos. 3,972,979 and 4,053,557 describe the decomposition of halogenated hydrocarbons by oxidation over chromium oxide or a boehmite supported platinum.
U.S. Pat. Nos. 4,059,675, 4,059,676 and 4,059,683 describe methods for decomposing halogenated organic compounds using catalysts containing ruthenium, ruthenium-platinum and platinum, respectively, in the presence of an oxidizing agent at a temperature of at least 350.degree. C.
The article by James J. Spivy, "Complete Catalytic Oxidation of Volatile Organics", Ind. Eng. Chem. Res., 1987, 26, 2165-2180, is a review of the literature dealing with the heterogeneous catalytic oxidation of volatile organic compounds.
The article by S. Chatterjee and H. L. Green, "Oxidative Catalysis by Chlorinated Hydrocarbons by Metal-Load Acid Catalysts", Journal of Catalysis, 1991, 130, 76-85, reports on a study of the catalytic oxidation of methylene chloride in air using supported zeolite catalysts H--Y, Cr--Y, and Ce--Y.
The article by A. Melchor, E. Garbowski, M. V. Michel-Vital Mathia and M. Primer, "Physicochemical Properties and Isomerization Activity of Chlorinated Pt/Al.sub.2 O.sub.3 Catalyst", J. Chem Soc., Faraday Trans. 1, 1986, 82, 3667-3679, reports that chlorination of alumina leads to a very acidic solid because of an enhancement of the strength and the number of strong Lewis Sites. The chlorination treatment enhances the sintering of platinum.
U.S. Pat. No. 4,983,366 describes a method for the catalytic conversion of waste gases containing hydrocarbons and carbon monoxide by passing the waste gases through a first zone containing a catalyst such as aluminum oxide, silicon dioxide, aluminum silicate and/or a zeolite optionally containing oxidic compounds or barium, manganese, copper, chromium, and nickel, and then through a second zone containing a catalyst such as platinum and/or platinum and/or palladium or platinum and rhodium.
PCT International Application No. PCT/US90/02386 describes a catalytic process for converting or destroying organic compounds including organohalogen compounds using a catalyst which contains as a catalytic component titania. The preferred catalyst also contains vanadium oxide, tungsten oxide, tin oxide; and at least one noble metal selected from the group consisting of platinum, palladium, and rhodium characterized in that the vanadium oxide, tungsten oxide and noble metals are uniformly dispersed on the titania.
U.S. Pat. No. 5,283,041 (commonly assigned to assignee of the instant invention), hereby incorporated by reference, discloses an oxidation catalyst for treating a gas stream containing compounds selected from the group consisting of halogenated organic compounds, other organic compounds and mixtures thereof. The catalyst comprises a core material of zirconium oxide and one or more oxides of manganese, cerium or cobalt with vanadium oxide dispersed thereon, and may further include a platinum group metal dispersed on the core material.
There is still a need for catalysts for the oxidative destruction of halogenated organic compounds, non-halogenated and carbon monoxide to provide enhanced operating efficiencies at lower operating temperatures. This is particularly true for the treatment of gas streams containing organobromides, which have been found to be particularly difficult to incinerate.